Folder.Maildir: Simplify getmessagetime

No need to use os.stat()['st_mtime'] when there is os.path.getmtime()

Signed-off-by: Sebastian Spaeth <Sebastian@SSpaeth.de>

offlineimap/folder/Maildir.py

@@ -205,8 +205,7 @@ class MaildirFolder(BaseFolder):
     def getmessagetime(self, uid):
         filename = self.messagelist[uid]['filename']
         filepath = os.path.join(self.getfullname(), filename)
-        st = os.stat(filepath)
-        return st.st_mtime
+        return os.path.getmtime(filepath)
 
     def savemessage(self, uid, content, flags, rtime):
         # This function only ever saves to tmp/,